1. Field of the Invention
This invention relates to anhydride-functional polymers obtained by polymerizing, under free radical addition polymerization conditions, (i) an alkenyl succinic anhydride having the structure: ##STR2## wherein R.sub.1, R.sub.2 and R.sub.3 are each independently hydrogen or alkyl or substituted alkyl of 1 to about 30, preferably 1 to about 8 carbons; and (ii) at least one (meth)acrylic unsaturated monomer copolymerizable with the alkenyl succinic anhydride; and, optionally, (iii) at least one other copolymerizable ethylenically unsaturated monomer. The R.sub.1, R.sub.2 and R.sub.3 groups can be alkyl groups which are substituted with other groups such as phenyl, ethoxy or any other groups which are stable during the subsequent free radical polymerization of the alkenyl succinic anhydride. The anhydride-functional polymers should have an average of at least two anhydride groups per molecule.
The anhydride-functional polymers are useful as corrosion or scale inhibitors, thickeners, dispersants and as reactive agents and/or crosslinking agents for compounds having functional groups, such as epoxy, hydroxyl or amine groups, which are reactive with anhydride groups. The anhydride polymers can, therefore, be utilized in a variety of materials such as plastics, fibers, adhesives, paper sizing, inks and, particularly, coating compositions.
This invention also relates to novel reactive compositions which utilize the anhydride-functional polymer in combination with one or more other materials which can react with anhydride groups. These reactive compositions can be reacted at room temperature or force dried at temperatures ranging up to about 350.degree. F. or higher if desired. When utilized as reactive crosslinking agents for coatings, the anhydride-functional polymers may be utilized in a variety of coating applications, including primers and topcoats as well as clearcoats and/or basecoats in clearcoat/basecoat compositions.
The reactive compositions typically involve the combination of the anhydride-functional polymer with materials reactive with anhydrides such as polyepoxides, polyamines, polyols, etc. One preferred reactive composition comprises the anhydride-functional polymer and a polyol, preferably a hydroxy-functional polymer, optionally in combination with an epoxide or polyepoxide. Another preferred reactive composition comprises the anhydride-functional polymer, an acid-functional compound, an epoxide or polyepoxide, and, optionally, a polyol. All of these combinations can provide fast reacting, durable coatings which minimize the toxicity problems which may be associated with other low temperature curing systems.
2. Description of the Prior Art
The reaction of alkenyl succinic anhydrides and selected olefins has been known in the art. Japanese examined patent application number 48-43191 teaches the Ziegler-Natta copolymerization of alkenyl anhydrides with olefins such as ethylene, butene or styrene, in the presence of a mixed catalyst comprising an organic metal compound and a transition metal compound. Japanese patents 01225964, 46027530 and 57080408 teach copolymers incorporating alkenyl succinic anhydrides. U.S. Pat. No. 4,374,235 teaches polymers obtained by the free radical initiated addition polymerization of an alkenyl succinic anhydride with one or more vinyl monomers such as maleic anhydride, maleimides, vinyl acetate, and alkyl vinyl ethers. U.S. Pat. No. 4,599,432 teaches the production of alkenyl succinic anhydride compositions by reaction of an olefin and maleic anhydride at temperatures ranging from 170.degree. C. to 260.degree. C., generally in the absence of a solvent, followed by the addition of a free radical catalyst to polymerize any unreacted olefin and maleic anhydride.
Unsaturated anhydrides, such as maleic anhydride, and copolymers made from maleic anhydride are known in the art. Such anhydride copolymers are heterogeneous with respect to the distribution of anhydride groups along the backbone of the polymer due to the abnormal copolymerization behavior of maleic anhydride with other monomers, and the acid groups generated from opening these anhydrides by reaction with hydroxyl or amine groups are not highly reactive for further cure reactions, e.g. with epoxy groups, due to steric hindrance arising from the proximity of the anhydride ring to the polymer backbone. Such anhydride-functional polymers are also relatively viscous and may be difficult to utilize in combination with low levels of solvent. Additionally, such polymers may form dark colored materials when certain base catalysts, such as N-methyl imidazole, are used to accelerate a subsequent reaction of the polyanhydride with reactive materials such as hydroxy-functional compounds.
Coating compositions comprising polyanhydrides in combination with other reactive materials are known in the art. For example, U.S. Pat. No. 4,946,744 teaches clearcoat/basecoat combinations involving (i) a polyanhydride, for example, such as that prepared by copolymerization of maleic anhydride with (meth)acrylic monomers, and (ii) a polyol. U.S. Pat. No. 5,227,243 teaches curable compositions comprising a polyanhydride, a polyol and an epoxy-functional compound. U.S. Pat. No. 4,871,806 teaches curable compositions comprising a polyanhydride, a polyacid, a polyol and an epoxy-functional compound. U.S. Pat. No. 4,859,758 teaches an acid-functional cellulose ester based polymer which could be used in combination with a polyanhydride and a polyepoxide. U.S. Pat. No. 4,927,868 teaches copolymers of alpha olefins and unsaturated anhydrides which could be used with a polyepoxide and, preferably, a polyacid.